1. Field of Invention
The present invention relates to voltage stabilizing magnetic core transformers of the type used to energize gas filled lamps and lighting tubes.
2. Background Art
Magnetic transformers have been used for voltage regulation in the ballast circuits of fluorescent and other gas filled discharge lamps for a number of years. The problems associated with the use of magnetic core transformers for this purpose usually involve the high cost of the iron and copper materials used in the manufacture of these devices. These problems are aggravated by the fact that proper operation of a voltage regulator or stabilizing transformer requires a magnetic shunt and air gap in the magnetic circuit of the transformer, which complicates the shape of the iron core elements.
One solution to the above problems has been to assemble the magnetic core from magnetic sheets or stampings which include the shunt as an integral part of the central winding core. An example of this type of construction is found in Spanish Pat. No. 352,884 of Aug. 1, 1969. That patent discloses a transformer of essentially square cross-section with a stack length governed by the formula that the ratio of the stack length to twice the sum of the sides of the stack cross-section is equal to or greater than 0.25 and wherein the coils are wound in a plane parallel to the stack length. In addition, the shunt piece is an integral part of the winding core thus providing a shorter magnetic circuit length and greater dispersion through the shunt as opposed to the windings. This design is said to produce significant improvements in stabilization over previous designs when used with a capacitive reactance in the secondary circuit.
FIGS. 1 and 2 show the two types of magnetic stabilizers that are presently used and manufactured. These two types of magnetic stabilizers are basically the same in concept, the use of either depending on the dimensions of the lamp or tube for which they are to be employed. As can be seen in these figures, the physical difference is in dimension "A", which solely affects the length of the magnetic circuit, the magnetic core section being the same in both models.
The stabilizing transformer of the present invention provides a significant improvement over existing designs in that the stack length is much greater than in previous designs and is technically and economically determined by optimizing the stack length in terms of operation and material costs, this is combined with a floating magnetic shunt, both of which providing a greater leakage inductance variation with respect to the primary voltage and thus a much wider range of stabilization.